Sb3+ and Er3+ co-doped Cs2NaYCl6 double perovskite with ultra-high sensitivity for optical thermometry

Optical thermometry has attracted great attention because it enables accurate temperature measurement in harsh environments due to non-contact temperature measurement. Three-dimensional (3D) lead-free halide perovskites have a great application potential in this field, due to its outstanding luminous properties and stability. In this work, the Sb3+ and Er3+ are introduced in Cs2NaYCl6 double perovskites (DPs). The Sb3+ doping Cs2NaYCl6 DPs exhibits bright blue emission from the Sb3+ activated self-trapped excitons (STEs) and Sb3+,Er3+ co-doped Cs2NaYCl6 has efficient green emission with excellent photoluminescence quantum yields (PLQY) of 81.1% because of the presence of energy transfer from self-trapped excitons to Er3+ ions. Excitingly, the ratio between the fluorescence intensity at 524 nm and 550 nm (FIR(I524 nm/I550 nm)) and the ratio between the fluorescence intensity at 524 and 456 nm (FIR(I524 nm/I456 nm)) both have a high correlation with temperature in the range of 298–473 K. The maximum of relative sensitivity values reach to 1.18%/K (I524 nm/I550 nm) and 1.19%/K (I524 nm/I456 nm) at 298 K, respectively. The outstanding temperature sensitivity suggests that the Sb3+,Er3+ co-doped Cs2NaYCl6 has enormous application potential in ratiometric optical thermometry.